The section introduces aspects that may be helpful in facilitating a better understanding of the invention. Accordingly, the statements of this section are to be read in this light and are not to be understood as admission about what is in the prior art.
A printing apparatus for printing label paper includes a label paper driving mechanism, which is for transporting the printing material. The printing material is a strip of multiple consecutive self-adhesive labels which is wind up to a roll. The roll includes a backing strip, the so-called liner paper, wherein the labels are stuck to the backing strip and are separated from one another. Self-adhesive label paper rolls without a backing strip, the so-called linerless label paper rolls, include a running, adhesive strip of printing material. The label paper roll is unwind in the printing apparatus and transported by the label paper driving mechanism through the printing apparatus to a print head. The print head prints information on the label paper and then, the label is ejected in an eject section of the printing apparatus. For both cases, liner and linerless label paper, the paper is transported by a driven roller, which is a platen roller or a drawing off roller. Further rollers exist for defining the path of the label paper through the printing apparatus. During time and by printing multiple labels, especially driven rollers are subject to wearing and thus need to be replaced from time to time.
A printing apparatus is known from EP1278641B1. The printing apparatus has multiple rollers in a paper driving mechanism. In case of wearing of the rollers, they can be replaced conveniently and without tools by an operator.
The question how to determine if a roller needs to be replaced is not really addressed in the art. Common methods are to replace certain parts of the printing apparatus after a certain time or a certain number of operating hours. As the wearing is subject to the size and quality of the label paper, the quality of the rollers and the printing apparatus itself and other parameters like printing speed and the like, such a time cannot be exactly determined and there is a risk that parts are replaced to early or too late. Other methods are that if the printed image shows some defects, certain parts of the printing apparatus, which are subject to wearing, are replaced. In this case, a number of labels have been printed and do not have an adequate quality.